The invention relates generally to a method and apparatus for positioning a catheter relative to a junction in a hollow anatomical structure, such as a vein, including but not limited to, superficial and perforator veins, hemorrhoids, and esophageal varices. The catheter can include an electrode device having multiple leads for applying energy to the anatomical structure to cause it to durably assume a ligated form.
The human venous system of the lower limbs consists essentially of the superficial venous system and the deep venous system with perforating veins connecting the two systems. The superficial system includes the long or great saphenous vein (GSV) and the short saphenous vein. The deep venous system includes the anterior and posterior tibial veins which unite to form the popliteal vein, which in turn becomes the femoral vein (FV) when joined by the short saphenous vein. As illustrated in FIG. 1, The great saphenous vein (GSV) travels through the deep fascia and meets the femoral vein (FV) at the sapheno-femoral junction (SFJ).
The venous system contains numerous one-way valves for directing blood flow back to the heart such as those valves 20 located in the vein 22 shown in FIG. 1. The arrow leading out the top of the vein represents the antegrade flow of blood back to the heart. Venous valves are usually bicuspid valves, with each cusp 24 forming a sack or reservoir 26 for blood which, under retrograde blood pressure, forces the free surfaces of the cusps together to prevent retrograde flow of the blood and allows only antegrade blood flow to the heart. Competent venous valves prevent retrograde flow as blood is pushed forward through the vein lumen and back to the heart. When an incompetent valve 28 is in the flow path, the valve is unable to close because the cusps do not form a proper seal and retrograde flow of the blood cannot be stopped. When a venous valve fails, increased strain and pressure occur within the lower venous sections and overlying tissues, sometimes leading to additional valvular failure. Incompetent valves may result from the stretching of dilated veins. As the valves fail, increased pressure is imposed on the lower veins and the lower valves of the vein, which in turn exacerbates the failure of these lower valves. A cross-sectional perspective view of a dilated vein with an incompetent valve 28 taken along lines 2-2 of FIG. 1 is illustrated in FIG. 2. The valve cusps 24 can experience some separation at the commissure due to the thinning and stretching of the vein wall at the cusps. Two venous 10 conditions which often result from valve failure are varicose veins and more symptomatic chronic venous insufficiency.
The varicose vein condition includes dilation and tortuosity of the superficial veins of the lower limbs, resulting in unsightly discoloration, pain, swelling, and possibly ulceration. Varicose veins often involve incompetence of one or more venous valves, which allow reflux of blood within the superficial system. This can also worsen deep venous reflux and perforator reflux. Current treatments of vein insufficiency include surgical procedures such as vein stripping, ligation, and occasionally, vein-segment transplant.
Chronic venous insufficiency involves an aggravated condition of varicose veins which may be caused by degenerative weakness in the vein valve segment, or by hydrodynamic forces acting on the tissues of the body, such as the legs, ankles, and feet. As the valves in the veins fail, the hydrostatic pressure increases on the next venous valves down, causing those veins to dilate. As this continues, more venous valves will eventually fail. As they fail, the effective height of the column of blood above the feet and ankles grows, and the weight and hydrostatic pressure exerted on the tissues of the ankle and foot increases. When the weight of that column reaches a critical point as a result of the valve failures, ulcerations of the ankle begin to form, which start deep and eventually come to the surface.
Varicose veins can be treated by intra-luminal Ligation. As used herein, “ligation” or “intra-luminal ligation” comprises the occlusion, collapse, or closure of a lumen or hollow anatomical structure by the application of energy from within the lumen or structure. As used herein, “ligation” or “intraluminal ligation” includes electro-ligation. An electrode device is introduced into the lumen and RF energy is applied to the wall by the electrode device to ligate or close off the lumen.
The ligation treatment is often commenced at the sapheno-femoral junction (SFJ) in order to close down the tributaries in the region and prevent the subsequent development of alternate flow paths which can lead to recurrent varicosities. Improper placement of the catheter past the SFJ and into the femoral vein could cause heating of the blood or vein walls in the deep venous system.
The location of a catheter within the body of a patient is routinely detected by the use of imaging equipment, such as ultrasound or X-ray equipment. The imaging equipment allows the operator to place the electrode catheter near the SFJ. Such a procedure, however, requires transportation of the patient to an ultrasound or X-ray facility or, conversely, transportation of the ultrasound or X-ray equipment to the patient. Such imaging equipment is bulky, requires an additional person to operate the equipment, and can be time consuming to use. This can be both inconvenient and costly. Physiological factors can also interfere with the resolution of the system and prevent the acquisition of a clean image. Moreover, scheduling difficulties may arise based on the availability of the ultrasound facility or equipment, thereby delaying the minimally invasive treatment which would benefit the patient.
Although described above in terms of a vein, the concepts are generally applicable to other hollow anatomical structures in the body as well. The above description has been generally confined to veins in consideration of avoiding unnecessary repetition.
There is a need in the art for an apparatus and method for determining the location of a catheter near a junction of an anatomical hollow structure within the body of a patient which avoids the need for bulky imaging equipment. The present invention fulfills this and other needs.